Section 4: Using the Model 9100: Conductance Function 4.8-11
Final Width = 215mm
4.8.5.7 Spans of Source Currents
In the synthesized conductance technology used in the 9100, the constant current sourced from the UUT must fall within a maximum
of three spans of values for each dialled conductance value. The spans of constant source currents acceptable to the 9100, are shown
against their corresponding spans of output conductance in the following table:
Hardware Configuration Limits Constant Current Source Limits
on Span of Output Conductance UUTi Low UUTi High UUTi Super
02.5000 nS to 25.0000 nS 4nA to 32nA 2.5nA to 200nA N/A
025.001 nS to 250.000 nS 8nA to 32nA 25nA to 350nA 250nA to 3.5µA
0.25001 µS to 2.50000 µS 25nA to 320nA 250nA to 3.5µA 2.5µAto35µA
02.5001 µS to 25.0000 µS 250nA to 3.2µA 2.5µAto35µA25µA to 350µA
025.001 µS to 250.000 µS 2.5µAto32µA25µA to 350µA 250µA to 3.5mA
0.25001 mS to 2.00000 mS 25µA to 320µA 250µA to 3.5mA 2.5A to 35mA
When the Conductance function is entered from another function, the default conductance setting is 10µS, coupled with the default
current span of 'UUTi Low'. As the conductance span is altered within Conductance function, the 9100 will default to the current
span nearest to that previously in use. For instance, when using the ÷10 screen key to decrease the output setting from 200µS —
UUTi high current span (25µA to 350µA), the 9100 will automatically select 20µS — super current span (25µA to 350µA). If a
different Current span is required, it will be necessary to select it manually by pressing the CHANGE CURRENT screen key until
the chosen span is selected (refer to pages 4.8-2/3). The indications given on the screen for the three different spans are as follows:
UUTi Low UUTi High UUTi Super
U
U
T
i
U
U
T
i
U
U
T
i
Output Voltage Limitation
At any UUTi span, the 9100 will seek a suitable configuration of hardware to accommodate both the value of source current within
the limits, and the value of conductance set as Output Value. The maximum nominal output voltage is 10V, such that:
I
R
÷
G
T
=
≤
10V
Any Conductance value within the total span can be selected. However, if the source current exceeds the upper limit of the selected
span, the circuit will be saturated, and a warning will be given. Also, a warning will be given if the source current is less than the
lower limit. When a warning appears, the instrument will still function, but the specification will be compromised.
Always choose the lowest possible UUTi setting at which no 'Sense current high' warning appears; i.e. if a warning is given on a
particular UUTi span, work up to use the first span at which the warning disappears. Normally the 9100 toggles between just two
of the three possible settings. To force the third setting: turn the output off, make your selection, then turn the output back on.
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